National Organic Standards Board Technical Advisory Panel Review compiled by University of California Sustainable Agriculture Research and Education Program (UC SAREP) for the USDA National Organic Program Potassium Sulfate for use in crop production Executive Summary1 The following petition is under consideration with respect to NOP regulations subpart G, governing the inclusion of substances on the National List of Allowed and Prohibited Substances: Petitioned: Addition of potassium sulfate to section 205.601(j), “Synthetic substances allowed for use in organic crop production as plant or soil amendments.” Potassium sulfate is a source of highly soluble potassium, and has the additional benefit of supplying sulfur. It is used in agricultural production systems where potassium is a limiting nutrient and also as a substitute for potassium chloride on chloride- sensitive crops. The NOP has no prior ruling on the use of the substance. The nature of the petitioned substance is highly debatable. Naturally occurring potassium sulfate is not subject to the TAP review process because “naturally-occurring” substances are implicitly allowed for use in organics. The intended sourcing of the petitioned form of potassium sulfate, however, brings into question the interpretive distinctions between a “synthetic” and a “non-synthetic” under organic law. According to the petitioner, the product “should not be treated differently than product produced from natural brines” since it is produced from naturally occurring minerals. The crux of the decision to grant the petition rests on how one chooses to interpret this equivalency claim. All TAP reviewers agreed that the petitioned substance should be considered synthetic. In general, the reviewers also agreed that it should be restricted as a soil adjuvant. Two reviewers felt that the substance should not be added to the National List, while one reviewer felt that it should be added to the List with an annotation that restricts it use. The two reviewers who recommended that it not be added to the List felt that the substance was acceptable from a purely agrobiochemical standpoint, but that such an addition would run contrary to the principles of organic production practices. Summary of TAP Reviewer Analyses Synthetic/ Allowed or Notes/suggested annotations: Nonsynthetic Prohibited Synthetic (3) Allowed (1) Reviewer 1: Prohibition of the petitioned form of potassium sulfate as a soil adjuvant in organic Nonsynthetic (0) Prohibited (2) production, no annotation. Reveiwer 2: Addition of the petitioned form of potassium sulfate as an allowed synthetic, with an annotation that it be restricted to use on crops that are sensitive to chloride found in potassium chloride or in other potassium fertilizers containing excessive salts. Reviewer 3: Prohibition of the petitioned form of potassium sulfate as a soil adjuvant in organic production, no annotation. 1 This Technical Advisory Panel (TAP) review is based on the information available as of the date of this review. This review addresses the requirements of the Organic Foods Production Act to the best of the contractor’s ability, and has been reviewed by experts on the TAP. The substance is evaluated against the criteria found in section 2119(m) of the OFPA [7 USC 6517(m)]. The information and evaluation presented to the NOSB is based on the technical evaluation against those criteria, and does not incorporate commercial availability, socio-economic impact or others factors that the NOSB and the USDA may consider in making decisions. October 15, 2007 Page 1 of 11 NOSB TAP Review Compiled by UC SAREP Potassium sulfate – Production (general) Identification Chemical name: potassium sulfate CAS Number: 7778-80-5 Trade name: SOP, Other Codes: Other names: sulfate of potash, sulfuric EEC No.(EINECS/ELINCS) 231-915-5 acid dipotassium salt Characterization Composition: K2SO4 Physical Data (Merck 2002): Molecular weight: 174.26 g/mol Melting point: 1069°C Boiling point: 1689°C pH ≈7 Density: 2.332 g/cm3 Solubility: 1g dissolves in 8.3mL water, 4mL boiling water, 75 mL glycerol Solubility in water is decreased by KCl or (NH4)2SO4 Insoluble in alcohol, most organic solvents Stability: Stable under normal temperatures and pressures. If heated above decomposition temperatures (>700°C) toxic gases/vapors may be released (SOx, K2O). Hazardous Polymerization: Will not occur. Physical Properties: Colorless or white, odorless, hard, bitter crystals, or white granules or powder. The aqueous solution is neutral (Merck 2002). How Made: Potassium sulfate is refined from naturally occurring mineral salt deposits or by chemical synthesis. Naturally occurring potassium deposits, referred to indiscriminately as “potash”, are usually the source of one or more ingredients of synthetic production. The deposits are found as a conglomeration of potassium chloride (muriate of potash, KCl, or MOP), potassium sulfate (sulfate of potash, or SOP), and potassium nitrate (nitrate of potash, KNO3, or NOP). Deposits are predominantly mined, while some are obtained through solar evaporation of natural brines from saline lake beds. Potassium chloride is the most abundant mineral found in deposits. Individual potassium salts and any impurities are separated through physical dissolution processes. According to documents contained in the petition, industrial synthesis of potassium sulfate is a two-step process: first, ionic separation of mined potassium chloride and another sulfate-bearing salt (in this case, magnesium sulfate) via electrolysis, followed by the joining of potassium and sulfate ions in controlled lab settings at temperatures up to 120°C (Konigsberger and Eriksson 1999). As noted by the petitioner, the potassium chloride and magnesium sulfate used in production are obtained from natural sources (Andres 2001). Specific manufacturing processes employed by the petitioner are considered confidential and thus are not disclosed in detail. Specific Uses Potassium sulfate is commonly used as a specialty fertilizer on crops that are sensitive to soil chloride levels, such as potatoes, lettuce, tobacco, avocados, peaches, and legumes. It is also used in cases where chloride buildup may be problematic. Mined and synthesized potassium sulfate are identical, and thus are functionally interchangeable. Worldwide, almost all technical grade potassium sulfate production (>99%) is used in agriculture. The remaining SOP is used in a wide range of industrial uses and for manufacturing potassium alum, potassium carbonate, and glass (Horn 2000). Status History of Use: The term “potash” comes from the colonial practice of collecting wood ashes from large pots and using it for fertilizer, soap, gunpowder, and glass (Thompson, no date). Worldwide, sulfate of potash (SOP) production since the mid-eighties has been characterized by an up and down cycle. The latest upward trend ended in 1998 due to development of new SOP sources that outpaced demand, and a massive reduction of tobacco cropping acreage in the US (–21%) and China (-32%). According to industry representatives, the SOP market is characterized by major over-capacities in production, with further increases expected (Horn 2000). This fact, coupled with predicted decreases in demand, has necessitated the development of new markets. In the US, SOP accounts for four to six percent of total agricultural potassium sales (Thompson, no date). October 15, 2007 Page 2 of 11 NOSB TAP Review Compiled by UC SAREP Potassium sulfate – Production (general) Functionality: The primary function of potassium sulfate is as a readily available source of potassium (K), a primary nutrient taken up by plants in lager amounts than any other nutrient except N. The most important function of K is the activation of more than 80 plant enzymes (Tisdale et al 1999). It is also integral to a number of other plant processes including water relations and maintenance of plant turgor, ATP production, translocation of carbohydrates, and protein synthesis. As a result, K deficiencies cause numerous problems, from decreasing rates of photosynthesis (Smid and Peaslee 1976) to the weakening of straw in grain crops (Schulte 1975). K stress can also increase the incidence of crop damage due to bacterial and fungal diseases, insect and mite infestation, and nematode and virus infection (Tisdale et al 1999). In addition, potassium has important effects on quality factors such as size, shape, color, taste, shelf life, and fiber quality. In conventional agriculture, potassium sulfate is used mostly on potatoes, fruit, and tobacco, which are sensitive to high applications of chloride (Tisdale et al 1999). It offers several advantages as a specialty fertilizer: it is virtually free of chloride, it has a low salt index, its high solubility allows a great deal of flexibility in fertigation systems and for foliar application, and it also provides a trace source of sulfur. Regardless of farming practices, nutrients will be removed in produce and must be replaced to sustain production and fertility of the soil. In organic systems, soil solution K+ is replenished by inputs of plant and animal residues. The effectiveness of these inputs will vary according to soil type. Annual K additions to apple trees grown on an oxisol (highly weathered soil) maintained soil K levels higher than recommended without reducing fruit quality or storage life (Ernani et al 2002). The complete “Petition Justification Statement” is as follows: “The product has been regarded as a synthetic substance by OMRI despite of the